favourite_languages={
    'jen':'python',
    'sarah':'c',
    'edward':'ruby',
    'phil':'python',
}

for name in favourite_languages.keys():
    print(name.title())

friends=['sarah','phil']
for name in favourite_languages.keys():
    print(f"Hi,{name.title()}")

    if name in friends:
        language=favourite_languages[name]
        print(f"\t{name.title()},I see you love {language.title()}!")
#方法keys（）返回的是一个列表
if 'erin' not in favourite_languages.keys():
    print("Erin, please take our poll !")